Technical Field
The present disclosure relates to a motor.
Background Art
In recent years, quality of a power element has improved so that a large current can be controlled even with a compact power element, thus, a high output has become achievable even with a compact motor. However, heat generated by the power element increases accordingly. Effective heat radiation is therefore desired.
As a measure of heat radiation for a power substrate equipped with a power element to which a large current is applied, Japanese Unexamined Application Publication No. 2015-089151 discloses a method in which a power element mounted on a surface of a power substrate by means of a through hole provided at the power substrate is exposed to a heat sink on the reverse side of the power substrate, and a method in which a number of small through holes (with a diameter of about ϕ0.2 mm to ϕ0.8 mm) are provided directly under a power element of a power substrate or on the periphery of the power element and the heat is radiated through the through holes to the heat sink.
However, according to Japanese Unexamined Application Publication No. 2015-089151, with the above methods, it is required to enlarge the diameter of the through holes and to increase the number of the through holes in order to improve the efficiency of heat radiation. Accordingly, the area of the substrate is enlarged and the value of the product is decreased.
Japanese Unexamined Application Publication No. 2015-089151 explains furthermore that there has conventionally been a method of carrying out higher heat radiation of substrate material as a heat-radiating measure of a power substrate. More specifically, it is disclosed that, instead of a resin substrate (glass epoxy substrate) which is widely prevalent, broadly utilizable and low in price, a substrate is made of ceramic or aluminum.
Japanese Unexamined Application Publication No. 2015-089151 teaches however that replacing a substrate with a substrate made of ceramic or aluminum, increases the cost of the substrate (ca. 5 times in the same volume ratio).
The present disclosure is related to providing a motor with improved heat radiation performance while enlargement of a substrate and increase of cost of the substrate are prevented.